1. Field of the Invention
The invention relates in general to gas-insulated electrical equipment and more particularly to gas-insulated electrical equipment having particle trapping means disposed along the high potential conductors.
2. Description of the Prior Art
It is known to provide particle traps in low field regions of compressed gas-insulated transmission lines where conducting or semiconducting particles may be trapped and inactivated. The lower field region in gas-insulated transmission lines is located along the outer sheath or outer elongated cylindrical conductor. It has been common practice, therefore, in the prior art to install the particle traps along the surface of the outer sheath. In horizontally disposed transmission lines the particle traps are installed at the bottom of the outer sheath, where gravity and the electric field eventually force these conducting or semiconducting particles into the particle trap. In vertically disposed transmission lines it has been the practice in the prior art to again locate the particle trap along the vertical oriented outer sheath, with a conical deflecting shield having an apex end section located higher than a base end section, to provide a path so that again the forces of gravity act upon the loose particles to propel them along the conical surface until such time as the particle is adjacent the outer sheath where it is deactivated in a particle trap. However, it is often unavoidable in bushings and circuit breakers as well as gas-insulated substations and vertical compressed gas-insulated transmission lines to design an epoxy cone-mounted insulator with the apex pointed downward wherein the forces of gravity would urge falling particles away from the outer sheath towards the central conductor in the region of high electric field. Also, the electric field present between the outer and inner conductors may, under the influence of the electric field, cause particles to be propelled towards the inner conductor as, but not limited to, along the surface of an insulator. Accordingly, it would be desirable to provide some means for trapping the particles which may be present near the surface of the inner conductor before they would precipitate electrical breakdown across the electrical transmission line or other electric apparatus.